#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import asyncio,logging

import aiomysql

def log(sql,args=()):
    logging.info('SQL: %s' % sql)
@asyncio.coroutine
def create_pool(loop,**kw):
    logging.info('create database connection pool ...')
    global __pool
    __pool = yield  from aiomysql.create_pool(
        host=kw.get('host','localhost'),
        port=kw.get('port',3306),
        user=kw['user'],
        password=kw['password'],
        db=kw['db'],
        charset=kw.get('charset','utf8'),
        autocommit=kw.get('autocommit',True),
        maxsize=kw.get('maxsize',10),
        minsize=kw.get('minsize',1),
        loop=loop
    )

@asyncio.coroutine
def select(sql,args,size=None):
    log(sql,args)
    global __pool
    with (yield from __pool) as conn:
        cur = yield from conn.cursor(aiomysql.DictCursor)
        yield from cur.execute(sql.replace('?','%s'),args or ())
        if size:
            rs = yield from cur.fetchmany(size)
        else:
            rs = yield from cur.fetchall()
        yield from cur.close()
        logging.info('rows returned: %s' % len(rs))
        return  rs

@asyncio.coroutine
def execute(sql,args,autocommit=True):
    log(sql)
    with (yield from __pool) as conn:
        if not autocommit:
            yield from conn.begin()
        try:
            cur = yield from conn.cursor()
            yield from cur.execute(sql.replace('?','%s'),args)
            affected = cur.rowcount
            yield from cur.close()
            if not autocommit:
                yield from conn.commit()
        except BaseException as e:
            if not autocommit:
                yield from conn.rollback()
            raise
        return affected

def create_args_string(num):
    L = []
    for n in range(num):
        L.append('?')
    return ','.join(L)

class Field(object):
    def __init__(self,name,column_type,primary_key,defautl):
        self.name = name
        self.column_type = column_type
        self.primary_key = primary_key
        self.default = defautl

    def __str__(self):
        return '<%s,%s:%s>'%(self.__class__.__name__,self.column_type,self.name)

class StringField(Field):
    def __init__(self,name=None,primary_key=False,default=None,ddl='varchar(100)'):
        super().__init__(name,ddl,primary_key,default)

class BooleanField(Field):
    def __init__(self,name=None,default=False):
        super().__init__(name,'boolean',False,default)

class IntegerField(Field):
    def __init__(self,name=None,primary_key=False,default=0):
        super().__init__(name,'bigint',primary_key,default)

class FloatField(Field):
    def __init__(self,name=None,primary_key=False,default=0):
        super().__init__(name,'real',primary_key,default)


class TextField(Field):
    def __init__(self, name=None, default=None):
        super().__init__(name, 'text', False, default)


class TextField(Field):
    def __init__(self, name=None, default=None):
       super().__init__(name, 'text', False, default)


class ModelMetaclass(type):
    def __new__(cls,name,bases,attrs):
        if name=='Model':
            return type.__new__(cls,name,bases,attrs)
        tableName = attrs.get('__table__',None) or name
        logging.info('found model:%s(table: %s)' % (name,tableName))
        mappings = dict()
        fields=[]
        primaryKey = None
        for k,v in attrs.items():

            if isinstance(v, Field):
                logging.info('  found mapping:  %s ==> %s' % (k,v))
                mappings[k] = v
                if v.primary_key:
                    if primaryKey:
                        raise Exception('Duplicate primary key for field: %s' % k)
                    primaryKey = k
                else:
                    fields.append(k)
        if not primaryKey:
            raise Exception('Primary key not found')
        for k in mappings.keys():
            attrs.pop(k)
        escaped_fields = list(map(lambda f: '`%s`' % f, fields))
        attrs['__mappings__'] = mappings
        attrs['__table__'] = tableName
        attrs['__primary_key__'] = primaryKey
        attrs['__fields__'] = fields
        attrs['__select__'] = 'select `%s`, %s from `%s` ' % (primaryKey, ','.join(escaped_fields),tableName)
        attrs['__insert__'] = 'insert into `%s` (%s, `%s`) values (%s)' %(tableName,
                                  ','.join(escaped_fields),primaryKey,create_args_string(len(escaped_fields) + 1))
        attrs['__update__'] = 'update `%s` set %s where `%s`=?' % (tableName,
                                ','.join(map(lambda f: '`%s`=?' % (mappings.get(f).name or f),fields)),primaryKey)
        attrs['__delete__'] = 'delete from `%s` where `%s`=?' % (tableName,primaryKey)
        return type.__new__(cls,name,bases,attrs)

class Model(dict,metaclass=ModelMetaclass):

    def __init__(self,**kw):
        super(Model,self).__init__(**kw)

    def __getattr__(self, key):
        try:
            return self[key]
        except KeyError:
            raise AttributeError(r"'Model' object has no attribute '%s'" % key)

    def __setattr__(self, key, value):
        self[key] = value

    def getValue(self,key):
        return getattr(self,key,None)

    def getValueOrDefault(self,key):
        value = getattr(self,key,None)
        if value is None:
            field = self.__mappings__[key]
            if field.default is not None:
                value = field.default() if callable(field.default) else field.default
                logging.debug('using default value for %s: %s' % (key,str(value)))
                setattr(self,key,value)
        return value
    @classmethod
    async def findAll(cls,where = None,args=None,**kw):
        ' find objects by where clause. '
        sql = [cls.__select__]
        if where:
            sql.append('where')
            sql.append(where)
        if args is None:
            args = []
        orderBy = kw.get('order by')
        if orderBy:
            sql.append('order by')
            sql.append(orderBy)
        limit = kw.get('limit',None)
        if limit is not None:
            sql.append('limit')
            if isinstance(limit,int):
                sql.append('?')
                args.append(limit)
            elif isinstance(limit,tuple) and len(limit) == 2:
                sql.append('?,?')
                args.extend(limit)
            else:
                raise ValueError('Invalid limit value: %s' % str(limit))
        rs = await select(' '.join(sql),args)
        return [cls(**r) for r in rs]

    @classmethod
    async def findNumber(cls,selectField,where=None,args=None):
        'find number by select and where. '
        sql = ['select %s _num_ from `%s`' % (selectField,cls.__table__)]
        if where:
            sql.append('where')
            sql.append(where)
        rs = await select(' '.join(sql),args,1)
        if len(rs) == 0:
            return None
        return rs[0]['_num_']

    @classmethod
    async def find(cls,pk):
        'find object by primary key. '
        rs = await select('%s where `%s`=?' % (cls.__select__,cls.__primary_key__),[pk],1)
        if len(rs) == 0:
            return None
        return cls(**rs[0])

    async def save(self):
        args = list(map(self.getValueOrDefault,self.__fields__))
        args.append(self.getValueOrDefault(self.__primary_key__))
        rows = await execute(self.__insert__,args)
        if rows != 1:
            logging.warning('failed to insert record：affected rows: %s' % rows)

    async def update(self):
        args = list(map(self.getValue,self.__fields__))
        args.append(self.getValue(self.__primary_key__))
        rows = await execute(self.__update__,args)
        if rows !=1:
            logging.warning('failed to update by primary key: affected rows: %s' % rows)

    async def remove(self):
        args = [self.getValue(self.__primary_key__)]
        rows = await execute(self.__delete__,args)
        if rows !=1:
            logging.warning('failed to remove by primary key: affected rows: %s' % rows)


